The research outlined in this proposal deals with several aspects of biologically active compounds produced by microorganisms. The main emphasis is on the biosynthesis of a number of antibiotics. The methods to be used include feeding experiments with precursors labeled with radioactive isotopes, but also to a large extent the use of C13-labeled compounds in conjunction with C13 Fourier Transform NMR. Antibiotics to be investigated are pyrrolnitrin, chlorothricin, spectinomycin, dihydrophenylalanine and ketomycin. In addition, some structural work is proposed which involves the structure elucidation of litmomycin, a new antibiotic, and of carbomonensin, a bio-transformation product of the antibiotic monensin. Also within this project, some pilot studies will be carried out to explore some possibilities of developing screening methods for pharmacologically active compounds from microorganisms.